Field of the Invention
The present invention relates to a backlight unit and a liquid crystal display device including the same, and more particularly, to a direct type backlight unit and a liquid crystal display device including the same.
Discussion of the Related Art
Portable electronic devices, such as mobile terminals and notebook computers, typically include flat panel display devices. Liquid crystal display devices, plasma display panels, field emission display devices, light emitting diode display devices, and organic light emitting diode display devices have been studied as examples of the flat panel display device. Among flat panel display devices, the liquid crystal display device has advantages, such as a highly-developed mass-production technology, comparatively easy driving, low power consumption, high definition resolution, and large screen size.
Since liquid crystals do not emit light, a liquid crystal display device includes a separate light source, such as a backlight unit provided with light-emitting diodes (LED) on a rear surface to irradiate light toward the surface of the liquid crystal panel in order to display an identifiable image. Backlight units may be categorized into direct-type backlight units and edge-type back light units. In a direct-type backlight unit, light sources are arranged below a liquid crystal panel. In an edge-type backlight unit, a light source is arranged to face a side of a light guide plate and a plurality of optical sheets are arranged between the liquid crystal panel and the light guide plate.
FIG. 1 is a cross-sectional view illustrating a related art direct-type backlight unit.
As shown in FIG. 1, according to the related art direct type backlight unit, a reflector 3 and a plurality of light sources 4 are disposed in a bottom cover 1, and a diffuser plate 5 and a plurality of optical sheets 6 are supported by a guide panel 2 disposed on the bottom cover 1. As such, light generated from the plurality of light sources 4 is scattered and refracted through the diffuser plate 5 and the optical sheets 6 to be diffused toward an entire surface of a liquid crystal panel (not shown).
The liquid crystal display device that includes the related art backlight unit as shown in FIG. 1 has problems as follows.
The diffuser plate 5 of the related art backlight unit is disposed to be supported in direct contact with the guide panel 2. Therefore, the light generated from the plurality of light sources 4 cannot move toward the area where the diffuser plate 5 is in contact with the guide panel 2, thereby causing a dark area at a corresponding area.
Further, according to the recent trend, the need of development of a liquid crystal display device having a narrow bezel has been increased. In the related art liquid crystal display device, the area where the diffuser plate 5 is in contact with the guide panel 2 may be covered by a bezel. However, as a bezel width becomes narrow, some of the area where the diffuser plate 5 is in contact with the guide panel 5 may not be covered by the bezel, thus a problem comes up in that a dark portion D occurs at an edge area of the liquid crystal panel, as shown in FIG. 1.
As described above, according to the related art direct type liquid crystal display device, a problem arises in that a dark portion occurs at an edge area of the liquid crystal panel due to a non-uniform supply of light.
Also, the need of a display device having an ultra-large sized area has been increased as technology advances. A technology called a videowall or multivision display device for realizing an ultra-large sized screen using a plurality of display devices has been developed because it is difficult to realize an ultra-large sized screen of 100 inches or more through one display device.
The videowall or multivision display device is a display device that realizes a large sized screen by continuously arranging a plurality of display devices in horizontal and/or vertical directions. In this way, the multivision display device displays different images in each unit display device or displays one image in each unit display device by dividing one image into serval images.
When an image is displayed, the more important image portion is usually a center area of the display device, and a less important image portion is at an edge area of the display device. Therefore, when an image displayed in each unit display device of a multivision display device, a dark portion may occurs at the edge area of the corresponding unit display device, which would be at a center area of the multivision display device. Thus, there may be a problem in that the image portion at the center area, which may be a more important image portion, is deteriorated.
As described above, when an image is divided and displayed through each unit display device of the multivision display device, a dark portion may occur in the important center image portion, and a user may deem the dark area as a shortcoming in the quality of the display device.